Conventionally, a heat resistant laminated conveyor belt of such a construction as shown in FIGS. 4(A) and (B) is used in a corrugated board manufacturing apparatus (Patent Document 1).
In FIGS. 4(A) and (B), numeral 31 designates a belt core layer that has a thickness of about 0.5 mm. The belt core layer 31 is made by repeating several times such a step that a plain weave fabric of aramide fiber is impregnated with a polytetrafluoroethylene (PTFE) dispersion (suspension) and is then dried and sintered.
On the belt core layer 31 (on an outer surface side thereof), an adhesive layer 32 is formed. The adhesive layer 32 is a perfluoroalkoxyl (PFA) film layer having a thickness of about 25 μm. Further, on an outer surface thereof, a reinforcing layer 33 having a thickness of about 0.5 mm is formed.
The reinforcing layer 33 is made by repeating several times such a step that a knitted fabric of aramide fiber is impregnated with the PTFE dispersion and is then dried and sintered.
The heat resistant laminated conveyor belt so constructed is usually used as a pressing belt for use in a corrugated board manufacturing apparatus (single facer), for example, as shown in FIG. 5.
FIG. 5 is a schematic constructional view showing a mechanism for manufacturing a single faced corrugated board by a lamination method using a pressing belt. In FIG. 5, numeral 4 designates an upper corrugating roll that meshes with a lower corrugating roll 5. On the upper side of the upper corrugating roll 4 and in the vicinity thereof, two rolls 6a, 6b are arranged. An endless type pressing belt 7 is provided being wound around the two rolls 6a, 6b. 
In the system of FIG. 5, a core paper 8 (corrugating medium) is caused to pass through between the upper corrugating roll 4 and lower corrugating roll 5 and further between the upper corrugating roll 4 and pressing belt 7, as shown by arrow X. Also, a liner 9 is caused to pass through between the upper corrugating roll 4 and pressing belt 7, as shown by arrow Y. Thereby, the core paper 8 is corrugated along an outer surface of the upper corrugating roll 4 and a glue (not shown) is applied to a top of each corrugation of the core paper 8 so that the core paper 8 and liner 9 are bonded together to form a lamination and a single faced corrugated board 10 is manufactured.
It is to be noted that when the core paper 8 and liner 9 are caused to pass through between the upper corrugating roll 4 and pressing belt 7, by function of the rolls 6a, 6b and pressing belt 7, such a pressing force as shown by arrows Z is generated to act on the core paper 8 and liner 9. The conveyor belt shown in the Patent Document 1 relates to such a pressing belt.
Patent Document 2 provides a press-bonded belt having a layer construction comprising a core fabric (1), adhesive layer (2) and surface fabric (3), wherein the core fabric (1) is a seamless fabric using a heat resistant high strength fiber yarn, the surface fabric (3) is a woven fabric having an obliquely crossing warp and weft structure using a heat resistant high strength fiber yarn and an impregnated layer or coated layer of fluororesin is applied at least to the surface fabric (3). This belt is also used in the single faced corrugated board manufacturing apparatus, as in the Patent Document 1.
Patent Document 3 provides a steam permeable pressing belt comprising a substrate of metallic warp and weft. The warp comprises sets of warps, each set of warps including three warps, and an interval between adjacent two sets of warps is smaller than a width of each set of warps. A weft material is preferably softer than a warp material and each weft has notches in which the warps are arranged. This belt is also used in the single faced corrugated board manufacturing apparatus, as in the Patent Documents 1 and 2.                Patent Document 1: Japanese Utility Model Registration 2584218 (FIG. 4)        Patent Document 2: Japanese Laid-Open Patent Application 1999-105171        Patent Document 3: Japanese Laid-Open Patent Application 1999-216787        
In the heat resistant laminated conveyor belt of the construction shown in the Patent Document 1, as the belt surface fabric is soft as compared with a high hardness material, such as steel, and its surface shape is flat, if it is used as a pressing belt of a corrugated board manufacturing apparatus, the belt surface pressure at the time when the liner and corrugated core paper are pressed to be bonded together becomes low. Thus, there is a possibility to cause a bonding defect when the production velocity is elevated for manufacturing a single faced corrugated board.
The bonding ability of the liner and core paper at the corrugated board manufacturing time depends on a surface hardness and surface shape of the belt. Hence, by enhancing the belt characteristics, enhancement of the bonding ability can be achieved. In the heat resistant conveyor belt of the construction shown in the Patent Document 1, a belt surface reinforcing layer made by a PTFE coated knitted fabric of aramide fiber is used for which the PTFE coated knitted fabric is obtained by repeating several times such a step that a knitted fabric of aramide fiber is impregnated with a PTFE resin dispersion and is then dried and sintered and the abrasion resistance and rigidity thereof are enhanced by increasing the number of mesh of the knitted fabric.
However, the material of this reinforcing layer is of a cushioning nature and its surface shape is flat. Hence, the belt surface pressure at the time when the liner and corrugated core paper are pressed to be bonded together becomes low. Thus, when the production velocity for manufacturing the single faced corrugated board is elevated, there is a possibility to cause a bonding defect. Also, impregnation of the fluororesin into the reinforcing layer and drying and sintering thereof are needed and hence there is a problem that the manufacturing process becomes complicated.
In the belt shown in the Patent Document 2, as the surface thereof is covered by the film layer to become soft as compared with a high hardness material, such as steel, the belt surface pressure at the time when the liner and corrugated core paper are pressed to be bonded together becomes low so that there is a possibility to deteriorate the bonding performance. Also, impregnation, drying and sintering of the surface fabric are needed and hence there is a problem that the manufacturing process becomes complicated.
In the belt shown in the Patent Document 3, as the structure thereof is a one-layer structure in which metallic yarns are sewed together, the belt is weak against bending fatigues and the life thereof is extraordinarily short.